Wide Load: Fat-Tire Bikes Explained

Just like big tires, trends can take a long time to blow up. Consider the pathbreaking ­Pugsley, from alt-bike brand Surly. When introduced in 2005, the bike was unlike anything else out there. With 3.8-inch-wide tires, it rode like a jeep, plowing over anything in its way.

The bike was designed for riding across snowy trails, but soon turned up underneath ultra-distance explorers and noncyclists looking for a new way to exercise during the winter. “I don’t think anyone at Surly consciously thought, oh, this is going to be big,” says Adam Scholtes, product manager at the Minnesota-based brand.

Seven years later, the fat-bike craze is in full swing and everyone from boutique brands to global behemoths like Specialized and Trek want a piece of the action—and Surly alone now offers three distinct models. Despite the comical proportions of a fat bike, it takes only one ride to understand the category’s appeal. The 3.8-inch tires create a huge contact patch with the ground, grabbing up traction on slick and loose surfaces. They are heavier than most bikes and turn slowly, but speed isn’t the point. The massive volume of the tires allows you to run air pressures so low they barely register on a normal pump’s gauge. The resulting floatation enables them to roll over snow, sand, mud, wet roots, rocks, and other terrain that would otherwise be impassable.

Recent design advances have expanded the bikes’ appeal. Even the Pugsley was a leap forward from its fat-bike forebear, the 1991 Hanebrink Extreme Terrain. That dune-buggy-like model used 20-inch-diameter, 8-inch-wide tires to negotiate snow, sand, and slickrock, but the small wheels limited its appeal. Current offerings ride more like traditional bikes and have improved in other subtle but important ways. Single-ring drivetrains ­(especially new 1x11 systems) offer a wide range of gears without requiring a front derailleur, which can clog with snow and ice. Changes­ in frame geometry have made the bikes more maneuverable and easier to steer. And the latest models are finally starting to shed some weight. Borealis now makes a fat bike with carbon-fiber rims that weighs a shocking 22 pounds.

Just don’t get too excited about using a fat bike for everyday transportation. Explorer Mike Curiak has ridden thousands of miles on them and plans to use one on a 700-mile expedition to the Northwest Passage this summer. “Fat bikes take me places where people haven’t been, where normal bikes couldn’t go,” he says. But he’d never consider one for conventional trails. “An $800 hardtail with a suspension fork will ride a million times better,” he says.

Still, there’s plenty to love. Fatties have extended the riding season through winter in the northern half of the United States and, in towns with groomed snow trails, the bikes are becoming as popular as cross-country skis. In Minneapolis, where Surly is based, enthusiasts have created a race series. And shops everywhere are finding that the bikes’ unique ride entices novice riders, drawing new riders to the sport.

“Because the tires are less apt to slide in corners, lose traction on rocks, or fall into ruts on even normal trails, fat bikes are just harder to screw up on,” says Ben Witt, who owned Milltown Cycles in Faribault, ­Minnesota, before taking a job at Salsa. People would walk by his shop, spot a fat bike, and come in to ask what it was. “I’d tell them riding one makes you feel like you’re eight years old again,” he says. And that might ultimately be the fat bike’s biggest draw.

Even Curiak admits that the wide wheels are a little addictive, no matter how good a rider you are. “There is something brainstem-level fun about this,” he says.

Salsa Beargrease Carbon

Now available with a svelte carbon frame, the Beargrease feels quicker than it looks—and Salsa designed it for snow events like Alaska’s Iditabike. Unlike many fat bikes, this one puts the rider in an aggressive position. That could put too much weight on the front wheel—a hindrance on sand or snow—so the company tweaked the frame angles and tube lengths. Even on challenging terrain, I felt centered between the wheels and was able to float over obstacles. The Makwa carbon fork has proportions similar to models with suspension. A few small brands offer suspension forks for fat bikes, but no major suppliers have committed yet. If they do, the Beargrease will be ready.—Ron Koch

Specialized Fatboy

Fat bikes are made to glide over snow and ice, but I found the Fat Boy to be equally capable on sand and singletrack—after I adjusted my riding style. I stopped picking a line and let the 4.6-inch-wide tires float me over rocks and roots. Better still, I could explore new terrain, like the bank of a stream or a sandy wash. I had expected the big tires to feel sluggish, but the lightweight carbon fork made it easy to loft the front wheel over obstacles. The bike felt agile, even when I rode it on twisty trails at home in Pennsylvania. The big wheels slowed the steering, but added stability and let me drift through corners—a fun sensation no matter what kind of terrain I was riding.—Mike Yozell

Fatback Aluminum Deluxe

Fatback calls its bikes “all-terrain” models, which is a bold claim when you consider that the company is based in Anchorage, Alaska, and its backyard includes the Cook Inlet and Chugach Mountains. And if that’s not rugged enough, the town receives as much as 140 inches of snow a year. To create bikes that can handle such a wild and diverse terrain, the company gives them 190mm-wide rear axles and faster handling. The American-made frame also comes with rack mounts and can accommodate standard 29er wheels, if you decide to ride on ­hard-packed trails.

Our Aluminum Deluxe came with a carbon fork and 90mm-wide rims. The parts are ideal for riding in winter—the twist shifters are mitten-friendly, and fluidless mechanical disc brakes are easier to service than hydraulic models should they seize on the frozen tundra. The bike rode well on soft surfaces but felt at home on firmer terrain. In fact, there aren’t many places this versatile fat bike can’t go.—Matt Phillips

Surly Moonlander

Even among fat bikes, the Moonlander’s 4.8-inch-wide tires and 100mm-wide rims appear pleasantly plump. Those extra-wide wheels allow you to run ridiculously low air pressure—like 3 psi—so you can take the Moonlander places few other bikes can go.

Riding it requires you to adjust your style somewhat. The cranks are spread wide to clear the rear tire, so once in the saddle you might feel a little like you’ve mounted a horse. The bike’s massive wheels also make it harder to steer, especially at low speeds. Pick up the pace and the Moonlander responds with some agility; push it too hard, however, and this fat bike feels like a runaway bus. But for those who want to travel over heavy snow, deep sand, or explore those open spaces on a map where there are no trails, the Moonlander is a great choice.—Matt Phillips

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